A. Field of the Invention
The field of the present invention is optical communications. Specifically, the present invention is directed to a device and method for generating both RZ and CSRZ signals using only one optical modulator.
B. Description of the Related Art
Various ways are known to optically generate RZ (return to zero) and CSRZ (carrier suppressed return to zero) shaped signals for optical communications. As is known by those skilled in the art, both RZ and CSRZ signals have their benefits in optical communications. Depending upon the application, it may be preferable to use one type of signal shape over another. For example, CSRZ shaped signals may be preferable for use in DWDM (dense wave division multiplexing) applications. CSRZ signals have lesser bandwidth so, in narrow channel spacing configurations like DWDM, the use of CSRZ can be better than regular RZ in reducing linear and even non-linear crosstalk.
There are known solutions for generating both RZ and CSRZ shaped signals in the optical domain using multiple optical modulators as will be discussed in more detail herein. However, such modulators can be very expensive, and it is known that electrical modulation can be accomplished in a more inexpensive manner. There is at least one method known for shaping RZ signals using electronic modulation and only one optical modulator. This solution is also discussed in further detail herein. The main problem with this solution is that it is limited only to RZ signals and does not allow for the shaping of CSRZ signals. As discussed above, for certain applications it may be beneficial to have the ability to generate CSRZ shaped signals.